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Gram Amp 2 SE phono preamplifier
system component Stereophile October 2002
Gram Amp 2SE is a professional-audio design based upon Graham Slee Projects'
concept of phase integrity. You'll hear stunning musicality, fluidity,
definition, delicacy and transparency without grain or edginess!
Gram amp 2 SE designer, Graham Slee, has worked at the highest end of pro-audio design - broadcasting. This experience includes designs used by the UK's national and international broadcasting organization, the BBC. A vinyl enthusiast with a varied collection (from rock to classical) he prefers listening to real vinyl than taped copies. He also has an in depth knowledge of record reproduction technology, from the disc cutting stage to playback in the studio or home. Graham has worked in hi-fi too.
In this light, the Gram amp 2 SE phono preamplifier he designed and crafts personally by hand are going to give you vinyl reproduction limited only by turntable, tone-arm and cartridge performance.
The signal from a record is the result of careful engineering to make the grooves a uniform size so that a stylus can track them easily. Retrieving the signal from the groove takes exact engineering to restore the sound back to the original so it can be transferred to the input of a preamplifer or amplifier.
All records are cut with falling bass (LF) and rising treble (HF) below and above some mid-range frequency (MF). It is this method that makes it possible to keep the groove a constant width. The mid-range frequency about which the equalization takes place varies somewhat depending on the format: 78's have many recording characteristics. So do early American and British microgroove LP's, then there's the up-to-date RIAA characteristic used on all modern records.
It is the phono preamplifier's function to perform the exact opposite effect to that of the record cutting machine. This is called equalization (EQ for short), which boosts the bass and cuts the treble by just the right amount. It also has to amplify the tiny signal from the pick-up cartridge, with minimal noise and distortion, so it's big enough to drive an amplifier.
Virtually all modern records are recorded to the RIAA standard and require RIAA equalization. But older records, and not just 78's, were recorded to different characteristics. Pre '60's LPs were recorded to the now redundant Decca/London FFRR, HMV/EMI, Columbia (British), Columbia (American) or NAB "standards". From 1955 most record companies changed over to the RIAA (new orthophonic) standard, but some companies kept their old "standards" well into the '60's because they considered them close enough to RIAA when listened to with record players of the era.
Broadcasting organizations, production studios and music lovers with large record collections will probably have lots of older records to the old "standards" that require their own equalization to play faithfully. RIAA equalization gives a passable approximation. If you want true fidelity however, you need the appropriate equalization circuit.
The Gram amp 2 SE is designed exactly and precisely for playback of RIAA recorded media. (We can supply by special order the Jazz Club phono preamp to restore the original tonal balance of older records - 78's early LP's and singles - as well as provide the highest fidelity reproduction of modern records and LPs.)
Gram amp 2 SE
Using his pro experience, Graham Slee set out to develop a high-gain phono stage fast enough to keep phase integrity as near to the original as possible and equally capable of handling transients. Phase integrity is about preserving the sound of things. The RIAA is accurate to within 0.5dB. The capacitors in the RIAA network of the 2 SE are very fast polypropylene types, faster than the precision polyprops. Several different polypropylene capacitors were auditioned in its development and the ones selected gave the best results in terms of timbre - both instrumental and vocal. There is a very slight tradeoff with this approach between precision and speed. The trumpet you hear may be up to half a decibel louder or softer than the original. It will however sound like a trumpet, which is better than having a trombone and trumpet sounding like one another. Moreover, since 1dB is the measure of the smallest difference we can hear, half a decibel is not really an audible difference in the real world.
Attention has also been paid to the input and output stages. A "special" type of capacitor discovery, which neither falls into the conventionally accepted electrolytic, tantalum, or film/foil categories, is used. This special capacitor allows much more musical information to pass through than even Elna audio grades. So for good measure this type is also used in the 2 SE's output stage.
The preamp can use moving magnet and high output moving coil cartridges with 2mV to 9mV output @ 5cm/sec velocity and at 9mV, still have 14dB of headroom. On recording studio equipment, the peak level is +8dB, and the other 6dB allows for replay of hot pressings, which are cut at greater velocity. With no rumble filter, the 2 SE has a frequency response from 10Hz - 150kHz (+/-3dB).
The Gram amp 2 SE is housed in a new silver case with four highly polished Teflon insulated gold plated phono sockets of the type usually only fitted to esoteric high-end gear. A plug-in wall DC power supply unit, overrated several times over, is used to supply power. The raw DC that the power supply provides is regulated properly inside the phono preamp.
Production of the 2 SE follows a set plan. All units have to be identical. Quality control is included in the design. Each unit is individually tested, first with a precision meter to ensure all voltages are correct and then with a broadcast quality professional audio test set. Tests are: (1) Noise - very revealing - at this point one can tell if most components are doing their job, and if a unit fails (rare, but it can happen), its usually an input cap or the chip - one or the other gets thrown. (2) Gain: both channels should match, if they don't it gets reworked. (3) Frequency response/RIAA accuracy: spot frequency test - should be within one quarter dB of the norm otherwise there's a cap out of spec. (4) Distortion: more than 0.03% is fail, but most hit 0.01% (1kHz) and the 2 SE first batch hit 0.008%. If any component is wrong it will fail the test. (5) Finally, each 2 SE is listened to.
Each unit is handcrafted. Handcrafted means what it says, everything is done by hand. Machines make the components and printed circuit boards, but that is before the 2 SEs are assembled. The boards are hand soldered using the finest Weller irons (the best you can buy), using the original "multicore" 60% tin solder. The final build is by hand, every thread is hand tightened - machines can't feel - all wires soldered on by hand. And finally, they're made in the designer's workshop. Then they're cleaned with a chamois leather, and wrapped.
The 2 SE Results
The 2 SE offers micro detail and weight, accuracy of timbre, better separation between performers, and a soundstage of great depth and breadth. It does not have the edginess of transistors or tubbiness of tubes. The 2 SE compares well with a number of expensive high-end phono preamps, due, in part, to its single stage topography and the attention paid to its fast performance. For those aspiring to high-end class and performance, the Gram Amp 2 SE offers an alternative within the coffers of many music lovers and serious record collectors.
Perhaps the best way to describe the Gram Amp 2SE's performance is by what reviewers say:
earmarks of a giant killer...the more you listen to this thing on its
own, the more you’ll discover that you can play it for hours without
fatigue...the presentation had a rare top to bottom cohesiveness, with
a tonal balance unusually rich, lush, and, well, beautiful...It’s
love at first sound between the Gram Amp and vocalists, while violins
are marvellously silken..."
"...the music the Gram
Amp 2 SE produced was very well tonally balanced. It was easy to listen
to but also imparted excitement without edginess. Amazingly, when partnered
with quite expensive frontends and 'speakers, the Gram SE was not left
wanting, it just played highly enjoyable music."
amazed by its sound...the Gram delivered genuine solidity in the mid-band
and mid-bass. It was quiet, and free from the thinness, edge, and grain
you usually get at this price..."
little machine. In the price versus quality sweepstakes, it is a winner
in every way that counts: musicality, definition, preservation of instrumental
and human voice timbre, speed, fullness of sound and, finally, price..."
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